Association Between 7 Years of Intensive Treatment of Type 1 Diabetes and Long-term Mortality

IMPORTANCE: Whether mortality in type 1 diabetes mellitus is affected following intensive glycemic therapy has not been established. OBJECTIVE: To determine whether mortality differed between the original intensive and conventional treatment groups in the long-term follow-up of the Diabetes Control and Complications Trial (DCCT) cohort. DESIGN, SETTING, AND PARTICIPANTS: After the DCCT (1983-1993) ended, participants were followed up in a multisite (27 US and Canadian academic clinical centers) observational study (Epidemiology of Diabetes Control and Complications EDIC) until December 31, 2012. Participants were 1441 healthy volunteers with diabetes mellitus who, at baseline, were 13 to 39 years of age with 1 to 15 years of diabetes duration and no or early microvascular complications, and without hypertension, preexisting cardiovascular disease, or other potentially life-threatening disease. INTERVENTIONS AND EXPOSURES: During the clinical trial, participants were randomly assigned to receive intensive therapy (n = 711) aimed at achieving glycemia as close to the nondiabetic range as safely possible, or conventional therapy (n = 730) with the goal of avoiding symptomatic hypoglycemia and hyperglycemia. At the end of the DCCT, after a mean of 6.5 years, intensive therapy was taught and recommended to all participants and diabetes care was returned to personal physicians. MAIN OUTCOMES AND MEASURES: Total and cause-specific mortality was assessed through annual contact with family and friends and through records over 27 years' mean follow-up. RESULTS: Vital status was ascertained for 1429 (99.2%) participants. There were 107 deaths, 64 in the conventional and 43 in the intensive group. The absolute risk difference was -109 per 100,000 patient-years (95% CI, -218 to -1), with lower all-cause mortality risk in the intensive therapy group (hazard ratio HR = 0.67 95% CI, 0.46-0.99; P = .045). Primary causes of death were cardiovascular disease (24 deaths; 22.4%), cancer (21 deaths; 19.6%), acute diabetes complications (19 deaths; 17.8%), and accidents or suicide (18 deaths; 16.8%). Higher levels of glycated hemoglobin (HbA1c) were associated with all-cause mortality (HR = 1.56 95% CI, 1.35-1.81 per 10% relative increase in HbA1c; P < .001), as well as the development of albuminuria (HR = 2.20 95% CI, 1.46-3.31; P < .001). CONCLUSIONS AND RELEVANCE: After a mean of 27 years' follow-up of patients with type 1 diabetes, 6.5 years of initial intensive diabetes therapy was associated with a modestly lower all-cause mortality rate when compared with conventional therapy. TRIAL REGISTRATION: clinicaltrials.gov Identifiers: NCT00360815 and NCT00360893.